Nicotine-antipsychotic drug interactions and attentional performance in female rats

Schizophrenia is marked by pronounced cognitive impairments in addition to the hallmark psychotic symptoms like hallucinations. Antipsychotic drugs can effectively reduce these hallucinations; however, the drugs have not resolved the cognitive impairment. Interestingly, nicotine, a drug commonly self-administered by people with schizophrenia, has been shown to significantly improve cognitive function of people with schizophrenia. The current study was conducted to determine the effect of typical (haloperidol) and atypical (clozapine and risperidone) antipsychotic drug treatment on sustained attention in rats performing a visual signal detection task. In addition, the interaction of haloperidol with chronic nicotine administration was assessed. Female Sprague-Dawley rats were injected subcutaneously with clozapine (0, 0.6, 1.25 and 2.5 mg/kg), risperidone (0, 0.025, 0.05 and 0.1 mg/kg) or haloperidol (0, 0.01, 0.02 and 0.04 mg/kg). In the second part of the study, the interaction of acute haloperidol (0, 0.005, 0.01 and 0.02 mg/kg) and chronic nicotine (5 mg/kg/day, for 4 weeks via osmotic minipump) was characterized. Clozapine, risperidone and haloperidol all caused dose-related impairments in percent hit performance. There was a significant linear dose-related impairment in percent hit caused by risperidone. All the doses of clozapine caused a significant impairment in percent hit at the higher luminance intensities in the visual signal detection task. The 0.01 and 0.02 mg/kg haloperidol doses caused significant decreases in percent hit. The 0.04 mg/kg haloperidol dose impaired performance of the task to the point that reliable choice accuracy measurements could not be made. Chronic nicotine infusion significantly diminished the impairing effects of haloperidol on performance during weeks 1-2. In summary, both typical and atypical antipsychotic drugs significantly impaired sustained attention in rats. Haloperidol was more detrimental than clozapine and risperidone. Chronic nicotine diminished the adverse effects of haloperidol on performance. This study establishes a paradigm to reliably determine the attentional impairment caused by antipsychotic drugs.